14Mhz CW Transceiver (250 mW)
Single Superheterodyne type (10 transistors + 1 IC)
I have modified 14Mhz Direct Conversion type CW transceiver to be single superheterodyne type.
It was very short time using DC type, I had only 5 QSO with DC type.
It was very thrilling QSO by DC type transceiver, I had many QRM without filter.
It was not bad but I have decided to modify.
Main specifications are as follows.
RX section : RF amp (2SK241) + Mixer (2SK439) + IF amp (3SK73) + DET (Quad Diode) + AF amp (2SC945 x 2)
TX section : LO 10.7Mhz (2SC1906), VXO 12.395Mhz (2SC1906), Mixer (SN16193P), Buff (Keying, 2SK241), Final (2SC2086)
I used existing final unit (2SK241 + 2SC2086) from old DC type transceiver.
VXO unit, I used super VXO with two xtal oscillators (12.395Mhz) and got coverage from 24.700 to 24.800 Mhz which mixed with 10.7Mhz and I could get 14.000 to 14.100 Mhz variable.
This time I used mixer IC SN16193P (Texas Instruments) to mix 10.7Mhz and 24.700.
Output power is about 250 mW at 13.8V.
Xtal filter is junk took from commercial HF transceiver which I purchased only Yen 1,000.
IF frequency is 10.7Mhz at receiving and 10.6993Mhz at transmitting.
700Hz shift is done by variable capacitor 1SV50.
Total 10 x transistors and 1 x IC, I used for this project.
You could see how different inside construction comparing to previous DC type transceiver.
I could hear each station without heavy QRM, xtal filter is very useful on HF band.
First QSO was JH9DRX/9, his RST599 and my RST529.
Sometiem I am using linear amplifier 5W (2SC1971) with this transciever.